What Is the Problem of Evil? A Philosophy Guide

The strongest form begins with a tension between divine attributes and the existence of evil. If a perfectly good being wants to prevent unnecessary suffering, an all-knowing being knows about it, and an all-powerful being can prevent it, why does so much suffering occur? The question can concern moral evil caused by human actions and natural evil such as disease, earthquakes, or other suffering not directly chosen by people.

This is the core of the problem of evil, but philosophers distinguish a logical problem from an evidential one. A logical argument tries to show that the traditional claims about God and evil cannot all be true together. An evidential argument is usually more modest. It argues that the amount or kinds of suffering we observe make such a God less likely.

One famous response points to free will. A world containing genuinely free moral agents may allow valuable love, responsibility, and choice, but that freedom also makes wrongdoing possible. This reply is aimed most directly at moral evil. It does not by itself explain every form of natural suffering, so additional arguments are often needed.

Another approach says difficult conditions can make courage, compassion, patience, and moral growth possible. This is sometimes called a soul-making response. Other thinkers argue that human knowledge is too limited to expect us to understand every reason a perfect being might have. Each reply changes how the problem of evil should be evaluated, but each also raises new questions.

Some philosophers respond by revising one of the traditional assumptions rather than offering a theodicy. They may question whether divine power should mean the ability to do anything logically possible, whether perfect goodness requires preventing every instance of suffering, or whether the concept of God should be understood differently. Others take the problem as evidence for atheism or agnosticism. Mapping these options shows why the debate continues across philosophy of religion rather than ending with one standard reply.

It helps to separate several issues instead of treating all suffering as one argument:

• •Is the argument claiming a contradiction or only evidence against a belief?
• •Does the response address moral evil, natural evil, or both?
• •Could the proposed good be achieved with less suffering?
• •How much weight should be given to limits in human knowledge?
• •Does the reply explain suffering or only show that an explanation is possible?

When studying the problem of evil, ask exactly what conclusion an argument is trying to establish. Showing that one proposed explanation is weak does not automatically prove the opposite worldview. Likewise, giving a possible reason for some suffering does not show that every case is justified. Careful philosophy compares the strength of the challenge with the strength and scope of each response.

The word theodicy, meaning a defence of God's justice in the face of evil, was coined by the philosopher Gottfried Wilhelm Leibniz, who published a book with that title in 1710. Leibniz argued that a perfect God would create the best of all possible worlds. Our world contains evil, he claimed, not because God could do no better, but because any world with as much overall good, including free creatures and rich variety, would have to contain some evil as part of the whole.

The argument faced a harsh test in 1755, when a great earthquake, followed by fires and a tsunami, devastated Lisbon on a religious holiday and killed tens of thousands of people. For many European thinkers the disaster made talk of the best possible world seem hollow. Voltaire wrote a poem on the catastrophe and later mocked Leibnizian optimism in his novel Candide. The episode shows natural evil driving the debate, since no human choice caused the earthquake itself.

Philosophers draw a useful distinction between a theodicy and a defence. A theodicy tries to give the actual reasons God permits evil. A defence aims at something smaller: it only needs to describe a possible situation in which God and evil both exist, showing that the two claims do not contradict each other. Alvin Plantinga's free will defence, developed in the 1970s, took this second route, and many philosophers, including some atheists, came to accept that the strict logical version of the problem had been answered.

That shifted attention to the evidential version, and William Rowe gave it a memorable form. He asked readers to imagine a fawn trapped in a forest fire started by lightning, badly burned and suffering for days before it dies, with no human ever knowing. It is hard to see what greater good this suffering could serve, and Rowe argued that such apparently pointless cases make the existence of God less probable. Replies often question whether our failure to see a reason is good evidence that no reason exists.

The problem is far older than modern philosophy. The Book of Job in the Hebrew Bible, usually dated by scholars to some point in the first millennium BCE, tells of a blameless man who loses his children, his wealth and his health. Three friends insist he must have sinned, since in their view suffering is always punishment. Job refuses to accept this and demands an answer from God. When God finally speaks from a whirlwind, he gives no reason for Job's suffering, but describes the vastness and wildness of a creation that Job could neither make nor fully understand.

Notably, the book ends with God rebuking the friends, which many readers take as a rejection of the idea that suffering always reveals guilt. A sharper philosophical version is traditionally credited to the Greek philosopher Epicurus: is God willing to prevent evil but unable, or able but unwilling? The attribution is uncertain, because the argument survives through the early Christian writer Lactantius rather than in Epicurus's own surviving works. David Hume gave it its best-known modern form in his Dialogues Concerning Natural Religion, published in 1779, where the character Philo repeats these old questions of Epicurus.

One of the most influential early responses came from Augustine of Hippo, who lived from 354 to 430. As a young man he followed Manichaeism, a religion teaching that the world is a battleground between two opposed powers, one good and one evil. After rejecting it, he argued that evil is not a thing God created at all but a privation, an absence of good that ought to be present, in the way blindness is a lack of sight rather than a substance in the eye. Moral evil, on his account, comes from free creatures turning away from God, and natural evil follows from that fall.

In 1966 the philosopher John Hick, in his book Evil and the God of Love, contrasted this Augustinian approach with one he traced to Irenaeus, a second-century bishop of Lyon. Irenaeus suggested that humans were created immature and must grow towards likeness to God, and Hick developed this into the soul-making idea, borrowing the phrase vale of soul-making from a letter by the poet John Keats. Critics see problems in both. Pain does not feel like a mere absence, and an account built on a historical fall is hard to square with evolution, which shows animals suffering and dying long before humans existed.

The problem of evil is a family of arguments asking whether the reality of suffering fits with belief in a perfectly good, all-knowing, and all-powerful God. Free will, moral growth, and limits of human understanding are among the major responses. The useful study habit is to identify which version of the problem is being discussed before judging any answer.